One type of conventional disc motor well-known in the art, such as that disclosed by Japanese Patent No. 3636700, mainly includes an output shaft, a substantially disc-shaped coil disc fixed to the output shaft and printed with a coil pattern, a commutator connected to the coil pattern, a magnet disposed in opposition to the coil pattern, and blushes for conducting an electric current to the commutator.
The rotating speed of the disc motor depends on the electric voltage conducted through the blushes, an electric current flowing to the disc motor, the coil pattern printed on the coil disc, a magnetic flux, the number of brushes (poles), and the like. When the electric voltages supplied through the brushes and the electric current flowing through the disc motor are constant, it is possible to set a desired rotating speed of the disc motor by changing the coil pattern of the coil disc, the magnetic flux, and the number of blushes.
When a disc motor is configured by laminating a plurality of coil discs each having two layers with which the coil pattern is printed, coil patterns on all layers are changed in order to achieve a desired rotating speed of the disc motor.